It is a hot afternoon at a lake house. The boat is plugged into the dock pedestal to keep the batteries topped up, the boat lift hums now and then, and the kids want one more jump off the end of the dock. Electric shock drowning (ESD) happens when electric current leaks into the water from a boat or dock, and a swimmer who enters that field can be paralyzed and drown without a mark on them.
In short: do not swim near any dock, marina or boat that has AC power. Tennessee’s State Fire Marshal advises staying at least 100 yards away and shutting off all shore power to the boat and dock before anyone swims off it. If a swimmer feels tingling, they should not swim toward the dock but warn others and back out the way they came. If someone is in trouble, do not jump in: shut off the power, call 911 and reach them from the dock. Have dock wiring installed and checked by a licensed electrician, and boats checked by a marine electrician trained to ABYC standards.
What electric shock drowning is
The Seattle Fire Department describes ESD as low-level alternating current (AC) passing through the body with enough force to cause skeletal muscle paralysis. It can occur anywhere electricity is provided near water, but the department notes that most ESD deaths have occurred around public and private marinas and docks. The source is usually a fault: a damaged cord, a corroded connection, a boat with a wiring problem, or dock wiring that was never meant to be wet.
Tennessee’s State Fire Marshal says ESD occurs when a swimmer unknowingly enters water electrified by a nearby power source: a swimmer can feel fine, then swim into the field.
Warning signs in the water
- Tingling, numbness or pain while swimming (named by Tennessee’s State Fire Marshal as signs of ESD).
- Muscle cramps or being unable to move (listed by the U.S. Consumer Product Safety Commission for electrified water).
- A swimmer near a dock or boat who suddenly struggles or goes quiet.
If you feel it yourself, Tennessee’s advice is: do not swim toward the dock, even though it is the natural thing to do. Warn others, stay upright, back out the way you came, and head for shore at least 100 yards from the dock. Have the owner cut power to the dock, and see a doctor afterward.
If someone is in the water: what to do
- Do not go in. “Fight the instinct to enter the water,” says Tennessee’s State Fire Marshal; many rescuers have died trying to help ESD victims.
- Shut off the power. At the meter base or breaker for the dock, or unplug the shore power cords. The CPSC warns that if the power stays on, rescuers can become victims too.
- Call for help. 911, or VHF channel 16 on the water.
- Reach, don’t wade. Once the power is off, get the person out from the dock. The CPSC cites the American Red Cross in recommending a fiberglass shepherd’s crook or rescue hook for electrified-water rescues.
- Start CPR if the person is not breathing or has no pulse, and continue until responders arrive.
No swimming near docks with AC power
Every authority we checked says the same thing in different words. NFPA: never swim near a marina, dock or boatyard, or near a boat while it is running, and obey all “no swimming” signs. Seattle Fire: never swim in or near marinas, docks or boatyards. Tennessee: never swim within 100 yards of any dock using electrical power, and shut off all shore power to the boat and dock before swimming off it. Tennessee also reminds owners that a neighbor’s dock can be the source, so it is worth working on this together along the shore.
NFPA adds one more: avoid entering the water when launching or loading your boat, because docks or boats can leak electricity into the water. For swimmers, our swimming from docks page covers the rest of the swim-zone rules.
How docks and boats are protected: GFCI, ELCI and the codes
On the dock. Dock and marina wiring is covered by the National Electrical Code (NFPA 70), Article 555, which deals with marinas, boatyards and commercial and noncommercial docking facilities and includes ground-fault protection rules for the circuits that feed them. The exact milliamp levels and which code edition applies depend on what your state and town have adopted. Washington, for example, ran its own timeline: its 2018 rule allowed 100 mA protection on feeders and 30 mA on branch circuits until September 1, 2019, when the 2020 NEC levels took over. We do not quote the code text beyond those public summaries; a licensed electrician and your local inspector will know the edition in force. Tennessee’s State Fire Marshal advises hiring a licensed electrician to wire the dock or check existing wiring, inspecting dock electrical systems at least once a year, and using a GFCI outlet if you charge boat batteries from the house or garage.
On the boat. The American Boat & Yacht Council’s standard E-11, “AC & DC Electrical Systems on Boats”, is the reference marine electricians work to (ABYC updated it in its 2025 supplement). Seattle Fire says boats with AC systems should have isolation transformers or equipment leakage circuit interrupter (ELCI) protection. Tennessee advises having the boat tested for leakage every year, installing an ELCI on the boat or in the shore power cord (or an isolation transformer), testing the ELCI monthly or as its maker says, using shore power cords built to UL standards rather than household extension cords, and never diving to work on underwater fittings while the boat is plugged in. NFPA adds: use only Marine Listed portable GFCIs or shore power cords, including “Y” adapters, and test GFCIs monthly.
Protection devices are not a substitute for keeping swimmers away. If a GFCI or ELCI keeps tripping, that is a fault to be found by an electrician, not a nuisance to bypass.
ESD checklist for dock owners
| Do this | Source |
|---|---|
| Post “no swimming” near any powered dock and keep swimmers 100 yards away | Tennessee SFMO, NFPA |
| Shut off all shore power to boat and dock before anyone swims | Tennessee SFMO |
| Licensed electrician for dock wiring; inspect at least once a year | Tennessee SFMO |
| Marine electrician checks the boat yearly and after a major storm | NFPA, Tennessee SFMO |
| ELCI or isolation transformer on boats with AC power | Seattle Fire, Tennessee SFMO |
| Marine Listed cords and portable GFCIs; test monthly | NFPA |
| Know where the breakers are; rehearse “power off first” | NFPA |
An inflatable dock has no wiring of its own, but it often sits beside a powered dock or lift. RAVE’s manual also asks owners to keep its dock away from engines and propellers. Read the rest of our dock and boating safety section, including storms and dock safety, since storms are when wiring gets damaged.
Electric shock drowning FAQ
How common is electric shock drowning?
There is no reliable national count we could cite. Deaths are often recorded as drownings, so we do not give a number.
Does salt water carry the same risk?
Tennessee’s 100-yard advice is written for freshwater marinas and docks, where the risk is greatest. Shock hazards still exist around any faulty wiring, so the same “no swimming near power” rule is the safe one everywhere.
Is a GFCI outlet on the dock enough?
It helps, but no agency we checked says it makes swimming near power safe. Keep swimmers away and turn power off before swimming.
Can I test my own dock for stray current?
Tennessee mentions that boat owners can check leakage with a clamp meter, but dock wiring testing and repair belong to a licensed electrician.